Motor vehicles employ heat exchangers to heat or cool various elements of an automotive engine and its component parts. Heat exchangers generally have a body part for exchange and may have heat exchanger tank parts, which can be described as being exchanger tanks which typically include a coolant and require a fluid tight seal. Heat exchanger tanks may be made of a variety of materials, depending on the strength and/or temperature requirements imposed upon them in automotive applications. Plastic tanks have been utilized in heat exchangers and have proven to reduce weight while providing good thermal and strength characteristics in a number of applications. Plastic header tanks, for example, as described in U.S. Patent publication No. US0141047A1, Lamick, published Jul. 31, 2003. However, due to the strict requirements imposed upon use of such tank parts in automotive applications, designs for plastic heat exchanger tank parts also use reinforcing ribs to enhance structural integrity and rigidity. In particular, these reinforcing ribs are normally oriented perpendicular or parallel to the plane of the header to achieve the desired characteristics. Ribs provide reinforcement by increasing the moment of inertia of the wall section where they are located. FIG. 1 shows a rib pattern typical in the prior art. Prior art designs, such as in FIG. 1, have been used for plastic heat exchanger radiator tank parts, with operating pressures high to low. In terms of fluid flow, however, the prior art designs are far from optimal to resist moderate to high operating pressures, particularly with their square or rectangular profile walls. Also, in automotive radiators, tanks with sidewalls that are essentially rectangular or uniform are often utilized.
Another, and, sometimes complementary solution to the reinforcing ribs of the prior art is to improve flow characteristics (pressure loss and flow distribution) by increasing flow area: this by increasing the tank part sidewall height. However, this has often led to the disadvantageous requirement for cross-ribs (i.e. ribs basically parallel to the header plane in many automotive applications) in the heat exchanger tank, particularly since the spacing between the tank foot and top wall bend (and hence the length of unsupported wall) necessarily increases. The potential solution of increasing sidewall height to deal with high pressure considerations also may disadvantageously complicate the molding process of the tank, since the mold tool cannot be simply removed in a direction perpendicular to the header unless all sidewall ribs are also perpendicular to the header.
Therefore, though increasing the sidewall height while maintaining a rectangular, i.e. uniform, profile would reduce pressure losses, the result is excessive tank volume near the ends. Excess tank volume is also known to degrade the transient response of the intake system (so called “turbo lag”). This solution is also not optimal from a materials and packaging standpoint.
The present invention overcomes these design weaknesses. By providing increased wall stiffening, the present invention is feasible in most all heat exchanger tank environments. The present invention has even further advantages as it relates to heat exchangers when fluid flow involves lower density liquids or where operating pressures are greater than moderate or even high to very high.